diff --git a/aoc2024.ps1 b/aoc2024.ps1
index bd6c791..c0e31c5 100644
--- a/aoc2024.ps1
+++ b/aoc2024.ps1
@@ -6,8 +6,8 @@ param (
     [switch] $All,
     [switch] $NoBuild,
     [ValidateSet(
-        "day1" , "day2"
-        # , "day3", "day4", "day5", "day6", "day7", "day8", "day9"
+        "day1", "day2", "day3"
+        # , "day4", "day5", "day6", "day7", "day8", "day9"
         # , "day10", "day11", "day12", "day13", "day14", "day15", "day16"
         # , "day17", "day18", "day19", "day20", "day21", "day22"
         # , "day23", "day24", "day25"
diff --git a/visp/examples/aoc2024/day1.visp b/visp/examples/aoc2024/day1.visp
index ce0e1b4..85401cf 100644
--- a/visp/examples/aoc2024/day1.visp
+++ b/visp/examples/aoc2024/day1.visp
@@ -1,4 +1,3 @@
-
 ;; Copyright 2024 Ville Penttinen
 ;; Distributed under the MIT License.
 ;; https://github.com/vipentti/visp-fs/blob/main/LICENSE.md
diff --git a/visp/examples/aoc2024/day2.visp b/visp/examples/aoc2024/day2.visp
index 5f41220..88c5d97 100644
--- a/visp/examples/aoc2024/day2.visp
+++ b/visp/examples/aoc2024/day2.visp
@@ -1,4 +1,3 @@
-
 ;; Copyright 2024 Ville Penttinen
 ;; Distributed under the MIT License.
 ;; https://github.com/vipentti/visp-fs/blob/main/LICENSE.md
diff --git a/visp/examples/aoc2024/day3.visp b/visp/examples/aoc2024/day3.visp
new file mode 100644
index 0000000..192cb08
--- /dev/null
+++ b/visp/examples/aoc2024/day3.visp
@@ -0,0 +1,87 @@
+;; Copyright 2024 Ville Penttinen
+;; Distributed under the MIT License.
+;; https://github.com/vipentti/visp-fs/blob/main/LICENSE.md
+;;
+;; for basic syntax highlighting
+;; vim: set syntax=clojure:
+
+;;
+;; day3
+;;
+;; Include common utlities
+(include "./common.visp")
+
+;; Functions & types
+(union Ins
+  [Mul [lhs: int] [rhs: int]]
+  Do
+  Dont)
+
+(fn ParseFile ([text: string])
+  ;; (mut lines (EnumerateSpanSplitLines text))
+
+  (let rx (new Regex "mul\((\d{1,3}),(\d{1,3})\)|do\(\)|don't\(\)" (.+Compiled RegexOptions)))
+
+  (let matches (.Matches rx text))
+
+  (mut pairs (||))
+
+  (for/in [mtch matches]
+    ;; (printfn "foo %A" (.+Value mtch))
+    (let val (+Value mtch))
+    (cond_
+      [(.StartsWith val "mul")
+        ()
+      (up! pairs (cons (Ins.Mul ((->> mtch +Groups .[1] +Value int) . (->> mtch +Groups .[2] +Value int)))))
+      ]
+      [(.StartsWith val "don't")
+        (up! pairs (cons Ins.Dont))
+      ]
+      [(.StartsWith val "do")
+        (up! pairs (cons Ins.Do))
+      ]
+    ))
+
+  (List.rev pairs))
+
+(fn Part1 (parsedInput)
+  ;; Implement part1
+  ;; (printfn "%A" parsedInput)
+  (->> parsedInput
+    (List.map #(match %1
+      [(Ins.Mul (lhs . rhs)) (lhs . rhs)]
+      [_ (0 . 0)]
+    ))
+    (List.fold #(+ %1 (* (fst %2) (snd %2))) 0)))
+
+(fn Part2 (parsedInput)
+  ;; Implement part2
+  ;; (printfn "%A" parsedInput)
+  (->> parsedInput
+    (List.fold #(begin
+      (let [(enabled, total) : bool * int] %1)
+      (match %2
+        [(Ins.Mul (lhs . rhs))
+          (if enabled
+            (enabled . (+ total (* lhs rhs)))
+            (enabled . total))
+        ]
+        [Ins.Do (true . total)]
+        [Ins.Dont (false . total)]
+      )
+    ) (true . 0))
+    snd
+  ))
+
+;; Implementation
+
+(let parsed (-> (ReadInput "day3") ParseFile))
+
+;; Expected results
+(let PART1_EXPECTED_RESULT (if IS_EXAMPLE 161 174561379))
+(let PART2_EXPECTED_RESULT (if IS_EXAMPLE 48 106921067))
+
+(WriteResult "part1" (-> parsed Part1) PART1_EXPECTED_RESULT)
+(WriteResult "part2" (-> parsed Part2) PART2_EXPECTED_RESULT)
+
+()
diff --git a/visp/examples/aoc2024/inputs/day3_example.txt b/visp/examples/aoc2024/inputs/day3_example.txt
new file mode 100644
index 0000000..30032cb
--- /dev/null
+++ b/visp/examples/aoc2024/inputs/day3_example.txt
@@ -0,0 +1 @@
+xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))
diff --git a/visp/lib/core.visp b/visp/lib/core.visp
index 0ebb910..a0adf03 100644
--- a/visp/lib/core.visp
+++ b/visp/lib/core.visp
@@ -12,6 +12,9 @@
         (failwithf "not valid number '%s'" it)
         (. result +Value)))
 
+(fn string->int32 [(it: string)]
+    (System.Int32.Parse it))
+
 (fn string->int [(it: string)]
     (System.Int64.Parse it))